Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$250.87	8.162%	$271.346	$271.35	$271.35	$271.30
Purchase #2	$82.29	9.781%	$90.3388	$90.34	$90.35	$90.30
Purchase #3	$30.54	3.446%	$31.5924	$31.59	$31.60	$31.60
Purchase #4	$119.87	6.732%	$127.9396	$127.94	$127.95	$127.90
Purchase #5	$62.60	5.779%	$66.2177	$66.22	$66.20	$66.20
Purchase #6	$213.44	13.366%	$241.9684	$241.97	$241.95	$242.00
Purchase #7	$65.53	3.169%	$67.6066	$67.61	$67.60	$67.60
7 purchase totals =	$825.14		$897.0095	$897.02	$897.00	$896.90